The invention relates generally to a seat belt status alerting unit and, more particularly, to such a unit for providing alert signals when a seat belt is buckled and unbuckled.
Seat belt warning devices are of particular potential benefit in the supervision of children riding in a vehicle. A seat belt status alerting unit, particularly one which provides an audible indication, can assist an adult in determining that a child has buckled his or her seat belt and, perhaps more importantly, can alert the adult when the child has unbuckled the seat belt.
Any such device necessarily must include a switch or sensor of some sort for determining when the seat belt is in use and when it is not, typically by sensing the insertion of a seat belt tongue into the corresponding buckle. A wide variety of seat belt buckle designs have been proposed incorporating a switch or sensor within the buckle for sensing the insertion and withdrawal of the seat belt tongue. Signals from such buckle switches typically are connected to vehicle wiring during manufacture, and may be employed to activate both audible and visual alarms, such as indicators on the vehicle dashboard.
Such buckles including switches or other sensors are of use only when actually present, typically by being provided as part of a vehicle. Moreover, they typically serve other primary functions rather than being specialized as a child seat belt safety warning device.
Accordingly, add on accessory seat belt safety warning devices have been proposed, such as are disclosed in Dear U.S. Pat. No. 5,406,252 and Bogar U.S. Pat. No. 5,627,512.
Dear U.S. Pat. No. 5,406,252 discloses a seat belt warning device in the form a self-contained electronic unit mounted externally to a seat belt buckle. A slider sensing element projects from the unit, and slot on the slider is engaged by a seat belt tongue as the tongue is inserted into the buckle.
Bogar U.S. Pat. No. 5,627,512 discloses a different approach to providing a seat belt warning device, in the form of a housing which at one end receives the existing seat belt tongue, and which at the other end has a new tongue which engages the existing buckle. The Bogar unit is thus mechanically connected in series between the existing seat belt tongue and buckle, and is positioned in an end-to-end relationship with the buckle when connected. A sensor switch projects from the end of the unit and engages the buckle as the new tongue is inserted into the buckle.
A shortcoming of both the Dear and Bogar approaches is a lack of universality, a significant requirement for an add-on device not part of the vehicle seat belt system as originally manufactured. Thus, there are a variety of different seat belt buckle designs among the many types of vehicles which have been manufactured, and it is difficult to provide an add-on device which works effectively with a wide range of these existing seat belt buckles and without interfering with normal usage.
For example, the slidable sensing element of the device disclosed in Dear U.S. Pat. No. 5,406,252 requires additional care on the part of the user to align the seat belt tongue with the slot on the slider element while inserting the tongue straight into the buckle. Seat belt users however typically start inserting a seat belt tongue into the corresponding buckle at an angle, and most seat belt buckles are designed to properly guide and align the tongue even though the tongue may have initially been inserted at an angle. Further, commercial embodiments of a device similar to that which is disclosed in Dear U.S. Pat. No. 5,406,252 are sold with adapters to accommodate various seat belt designs.
The approach of Bogar U.S. Pat. No. 5,627,512 is even less universal, because the new tongue of the Bogar device must be sufficiently similar to the existing seat belt tongue to assure proper latching operation, making the provision of a universal device rather unlikely with that particular approach.
Another consideration in such devices is providing a low battery indication. The device disclosed in Dear U.S. Pat. No. 5,406,252, during operation, emits three audible "beeps" over a duration of approximately one second when the seat belt tongue is inserted into the buckle, and emits a stream of beeps over an interval of approximately three seconds when the tongue is removed from the buckle. If no "beeps" are heard when the tongue is inserted, it is assumed that the battery is low, and must be replaced.